The present invention relates to contacts in semiconductor devices, and more specifically, to low resistance metal contacts to interconnects.
In semiconductor devices, a contact acts as a bridge between the semiconductor (e.g., silicon (Si)) and a low-resistance metal interconnect (e.g., copper (Cu)). The contact material is typically disposed in an opening (via) in a dielectric layer and is needed as a buffer because the metal interconnect is typically a material that reacts with the semiconductor. For example, Cu dissolves in Si such that a Cu interconnect requires a contact (e.g., tungsten (W)) between the Cu and the Si. As semiconductor devices are made smaller, the contacts are also smaller. Because less area results in more resistance, the smaller contacts have higher resistance.